Downhole drilling tool

ABSTRACT

A directional drilling tool includes a housing defining a central cavity for enabling the transmission of drilling fluid through the drill string. A motor contained in the housing includes a rotor-stator assembly, and produces eccentric motion of the rotor. An inverter or shock absorbing assembly disposed along the housing upstream from the motor functions to expend and contract the central cavity in response to fluid pressure changes produced by the drilling fluid flow. A valve assembly, comprising a multi-port flow head that rotates under influence of the motor and a multi-port flow restrictor, creates a varying pattern of pressure spikes in the drilling fluid as the ports of the flow head move into and out of alignment with the ports of the flow restrictor, which in turn induces a percussive effect and axial movement in the drill string.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to United States ProvisionalApplication No. 61/737,050 filed Dec. 13, 2012, the entirety of which isincorporated herein by reference.

TECHNICAL FIELD

The present invention relates to drilling tools, and in particular todown hole drilling assemblies for use in oil and gas recoveryapplications.

TECHNICAL BACKGROUND

In oil and gas production and exploration, downhole drilling throughrock can be accomplished with a downhole drill through which drillingfluid, conventionally referred to as drilling mud, is pumped. Thedrilling fluid assists in the drilling process by, for example,dislodging and removing drill cuttings, cooling the drill bit, and/orproviding pressure to prevent formation fluids from entering thewellbore.

Application of a vibrational and/or percussive effect, which can beaccomplished through the regulation of drilling fluid flow, can improvethe performance of the downhole drill. Examples of downhole assembliesproviding such an effect include U.S. Pat. No. 2,780,438 issued toBielstein, and Canadian Patent No. 2,255,065.

BRIEF DESCRIPTION OF THE DRAWINGS

In drawings which illustrate by way of example only embodiments of thepresent disclosure, in which like reference numerals describe similaritems throughout the various figures,

FIG. 1 is a lateral cross-sectional view of a drilling tool inaccordance with one embodiment of the present invention.

FIG. 2 is a lateral cross-sectional view of a segment of the drillingtool shown in FIG. 1.

FIG. 3 is a lateral cross-sectional view of a multi-port flow head inaccordance with one embodiment of the present invention.

FIG. 4 is a cross-sectional view of a port end of the multi-port flowhead of FIG. 3.

FIG. 5 is a lateral cross-sectional view of a flow restrictor and insertin accordance with one embodiment of the present invention.

FIG. 6 is a top plan view of the flow restrictor and insert of FIG. 5.

FIG. 7 provides axial cross-sectional views illustrating the alignmentof ports in an example embodiment in operation.

In the drawings, preferred embodiments of the invention are illustratedby way of example. It is to be expressly understood that the descriptionand drawings are only for the purpose of illustration and as an aid tounderstanding, and are not intended as a definition of the limits of theinvention.

DETAILED DESCRIPTION

The present embodiments and examples provide a drilling fluid flowcontrolling downhole tool for controlling the flow of drilling fluid ina drill string, and components of the downhole tool. In one embodiment,there is described a directional drilling tool forming part of a drillstring. The drilling tool includes a mandrel, and a housing extendingfrom the mandrel, to define a central cavity for enabling thetransmission of drilling fluid through the drill string. A motor, suchas a positive displacement motor or turbine driven assembly, iscontained in the housing and includes a rotor-stator assembly in amulti-lobe arrangement, the motor for producing an eccentric motion ofthe rotor. An inverter is disposed along the drill string housingupstream from the motor and is capable of expanding and contracting thecentral cavity in response to fluid pressure changes produced by thedrilling fluid flow. A multiport flow head depends from the rotor. Theflow head comprises a plurality of ports on a face thereof, theplurality of ports for permitting the transmission of drilling fluidtherethrough, the flow head adapted to rotate as the rotor rotates. Aflow restrictor is affixed to the drill string housing downstream fromthe flow head and directly abutting the face of the flow head. The flowrestrictor itself has a multi-port arrangement which includes aplurality of ports extending through the flow restrictor to permittransmission of drilling fluid therethrough. In operation, the rotationof the flow head on the flow restrictor creates pattern of pressurespikes within the central cavity as the ports of the flow head move intoand out of alignment with the ports of the flow restrictor, which inturn causes the inverter to expand and contract in a correspondingpattern. Due to the eccentric motion induced in the flow head and therelative configurations of the ports in the flow head and the flowrestrictor, the pattern of pressure spikes is polyrhythmic, and may beconsidered to be relatively arrhythmic compared to simpler flowrestriction arrangements utilizing, for instance, a single-portconfiguration controlling drilling fluid flow.

In this respect, before explaining at least one embodiment of theinvention in detail, it is to be understood that the invention is notlimited in its application to the details of construction and to thearrangements of the components set forth in the following description orillustrated in the drawings. The invention is capable of otherembodiments and of being practiced and carried out in various ways.Also, it is to be understood that the phraseology and terminologyemployed herein are for the purpose of description and should not beregarded as limiting.

All terms used herein are used in accordance with their ordinarymeanings unless the context or definition clearly indicates otherwise.Also, unless indicated otherwise except within the claims the use of“or” includes “and” and vice-versa. Non-limiting terms are not to beconstrued as limiting unless expressly stated or the context clearlyindicates otherwise (for example, “including”, “having”, “characterizedby” and “comprising” typically indicate “including without limitation”).Singular forms included in the claims such as “a”, “an” and “the”include the plural reference unless expressly stated or the contextclearly indicates otherwise. Terms such as “may” and “can” are usedinterchangeably and use of any particular term should not be construedas limiting the scope or requiring experimentation to implement theclaimed subject matter or embodiments described herein. Further, it willbe appreciated by those skilled in the art that other variations of thepreferred embodiments described herein may also be practiced withoutdeparting from the scope of the invention.

Referring to FIG. 1, there is shown a cross section of a drilling tool100 within a drill string, in accordance with one embodiment of thepresent invention. The drilling tool 100 described herein forms part ofa drill string (not all of which is shown in the accompanying drawings)for use in down hole drilling applications, and in particulardirectional or horizontal well drilling, in which wells are laterallydisplaced from the surface drilling location. The tool 100 describedherein is assembled from a number of discrete components and sections;however, as will be appreciated by those skilled in the art, some of thecomponents and sections described herein may be constructed as a singleunit and/or contained within a unitary housing. In drilling operations,fluid, such as drilling mud, is delivered through a flowbore of a drillstring to a drill bit disposed at a distal end of the drill string. Thetool 100 provides fluid communication from an upstream end of the drillstring to the drilling components mounted below the tool 100.

The tool 100 is mounted on the drill string via a mandrel 110. Themandrel 110 defines part of a shaft 105 that receives drilling fluid andprovides fluid communication with a motor 140, discussed below. Theupper end of the mandrel 110 may be coupled to a drill pipe (not shown),while the lower end of the mandrel 110 is received within an upperhousing 115 and extends through the upper housing into an invertersection 120. The upper housing 115 may serve as an adaptor to positionthe mandrel 110 within the inverter section 120. Sealing contact betweenthe upper housing 115 and the mandrel 110 in this example is providedwith a wiper and/or seals 117 positioned around the mandrel 110. Theinverter section 120 may be, or may function as, a shock sub in thedrill string.

The inverter section 120 comprises a housing 125, housing an inverterassembly 300. In the embodiment shown in FIG. 1, the inverter assembly300 is retained in an annular shaped conduit which surrounds a portionof the shaft 105. The mandrel 110 terminates with a piston 130positioned below the inverter assembly 300. The piston 130 is sized totravel axially within the interior diameter of the housing 125 underinfluence of the inverter assembly 300. The inverter section 120 isdisposed in fluid communication with the motor 140 via the piston 130,and is capable of expanding and contracting the volume of the shaft 105in response to fluid pressure changes exerted on the inverter assembly300 by operation of the downstream motor 140, explained in greaterdetail below. The inverter assembly 300 may comprise a mechanical springassembly, or equivalent means, which stores energy in response to anincrease in fluid pressure within the shaft 105, and releases the storedenergy in response to a decrease in fluid pressure within the shaft 105.

As mentioned above, the shaft 105 defined by the mandrel 110 and theinverter assembly 120 receives drilling fluid and is in communicationwith a motor 140. The motor 140 may be a positive displacement motorcomprising a rotor 150 disposed within a stator 155, such that the rotor150 rotates within the stator 155. In the example shown in FIGS. 1 and2, the stator 155 is integral with a housing that is connected to theinverter housing 125, although the stator 155 may be a component housedwithin a separate motor housing. Each of the rotor 150 and stator 155has a multi-lobe configuration in an unequal ratio, such as a 7:8 loberatio, although other lobe ratios such as 4:5 and 5:6 may be utilized.As those skilled in the art will understand, the unequal lobearrangement of the stator 155 and rotor 150 results in a staggeredeccentric motion of the rotor 150 vis-a-vis the stator 155 when motionis induced in the rotor 150 during operation.

A valve section 160 is provided downstream from the motor 140. In theexample of FIGS. 1 and 2, the valve section 160 includes a housing 170,a multi-port flow head 180 positioned within a valve housing 170, and aflow restrictor 220 with an optional insert 210 interposed between theflow head 180 and the flow restrictor 220. The flow head 180 comprises aplurality of ports 190 and is secured to the rotor 150 at a first end182, for example by a suitable male/female engagement, or equivalentmeans, or by coupling via a drive shaft (not shown). In the exampleimplementation, the flow head 180 is a separate component from the rotor150; the first end 182 is adapted as necessary to couple with the rotor150. In another implementation, the flow head 180 may be formedintegrally with the rotor 150.

As can be seen in FIGS. 2 and 3, the first end 182 is provided at oneend of a body 186 of the flow head 180. The body 186 terminates at acollar 200 which joins the body 186 with the second end 184. In theillustrated example, the first end 182, body 186, and second end 184 areintegrally formed. The second end 184, which in this example isgenerally circular in profile, includes a number of ports 190 extendingtherethrough. The outer diameter of the collar 200 is smaller than theouter diameter of both the body 186 and the second end 184, with theresult that when in place in the valve section 160, an annular chamber205 (indicated in FIG. 2) is defined by the external contours of theflow head 180 and the internal contour of the valve housing 170. InFIGS. 1 and 2, it can be seen that the motor 140 is in fluidcommunication with the chamber 205 and the ports 190 of the flow head180, and that the chamber 205 can receive drilling fluid as it flowsfrom the motor 140 towards the ports 190 of the flow head 180.

Turning to FIGS. 3 and 4, four ports 190 of two different sizes areprovided in the second end 184 of the flow head 180. The ports 190extend in a direction substantially parallel to the axis of the flowhead 180 and are preferably substantially cylindrical, or are otherwisecurvilinear in shape such that a continuous interior wall is formedwithin each port 190, so as to facilitate fluid flow and discourage mudbuild-up on the interior port walls. In this example, the ports 190 aregenerally regularly distributed around the center of the second end 184with the centers of the ports 190 being a substantially equal distancefrom the center of the flow head 180, and with pairs of ports 190 beingdiametrically aligned. It will be appreciated from the examplesdescribed herein that the configuration of the ports 190 may vary fromthe example depicted in the accompanying drawings by number, size,positioning, shape or profile, or by a combination of two or more ofthese factors. Variations in the configuration of the ports 190 may bedetermined in part based on drilling fluid weight and/or desired fluidpressure within the tool 100. As will be appreciated from the discussionof the operation of the tool 100 below, more or less than four ports 190may be provided, but it is preferable to utilize at least two ports 190of at least two different sizes to provide sufficient drilling fluidflow variation.

Returning to FIGS. 1 and 2, a flow restrictor 220 is positioned withinthe valve housing 170, adjacent or proximate to the flow head 180, anddownstream from the motor 140. The flow restrictor 220 may be coupled tothe interior of the valve housing 170 by threaded engagement. Inoperation, the flow head 180 is rotated in eccentric rotation by therotor 150, and the flow restrictor 220 remains stationary with respectto the flow head 180 and rotor 150.

In the embodiment shown in FIG. 5, the flow restrictor 220 is asubstantially cylindrical component with a plurality of ports 230extending therethrough that are generally parallel to the component'saxis, and in this example, generally equally spaced from the flowrestrictor 220's center. The ports 230 are preferably cylindrical or atleast generally curvilinear in shape. The flow restrictor 220 includesat least two ports 230 of at least two different sizes, as with theports 190 of the flow head 180. In FIG. 6, three ports 230 are shown,where two ports are substantially equal in diameter and a third is of alarger diameter. While the flow restrictor 220 could include four oreven more ports 230, in the illustrated example of FIG. 6, the fourthport 230 (shown in phantom) is completely closed off by use of a plug orhardened insert. This plug may be removable so as to make the fourthport 230 available. Again, as with the flow head 180, the number, size,positioning, and/or shape or profile of the ports 230 can be varied asdescribed above. In the embodiments depicted in the drawings, the ports190 and 230 range in diameter from approximately 9/16″ to 13/16″, thoughthese stated diameters are exemplary and not meant to be limiting. Tofurther give effect to the desired variations in drilling fluid flow,while the ports 190, 230 on the flow head 180 and flow restrictor 220may be equally radially spaced apart on each component, the ports on oneor both components are not in regular or diametric alignment with eachother; for instance, rather than providing the ports 190, 230 angularlyspaced at 90° or 180° as can be seen in FIGS. 4 and 6, on at least onecomponent at least one port 190 or 230 is offset so that the spacingbetween it and an adjacent port is more or less than either 90° or 180°.

In one implementation, the second end 184 of the flow head 180 and anupper face of the flow restrictor 220 are positioned so that they aresubstantially in contact, with the effect that their respective facesmay rub together as the flow restrictor 220 receives the thrust loadgenerated by the motor 140. Thus, an insert 210 is also provided in apreferably wear-resistant material. A substantially cylindrical insert210 is most clearly seen in FIGS. 2 and 5. Where the insert 210 is used,the flow restrictor 220 may be provided with a lip 225 around its upperface (i.e., the face that is adjacent or proximate to the flow head 180)defining a recess for receiving the insert 210. As can be seen in FIG.5, the recess is sized so that the upper face of the lip 225 and theinsert 210 are substantially flush. The flow head 190 may therefore rideon top of both the lip 225 and the insert 210 without substantialobstruction. The insert 210 is also provided with ports 215 thatgenerally correspond to the ports 230 of the flow restrictor 220, butwhich may or may not substantially obstruct the ports 230. In theparticular example shown in FIGS. 5 and 6, it can be seen that the ports215 of the insert 210 correspond generally in shape, position andarrangement with the ports of the flow restrictor 220, but thedimensions of the ports 215 are not equal to the dimensions of theircorresponding ports 230 in the flow restrictor 220. This can result inpartial obstruction of a port 230 when the port 215 of the insert 210 issmaller than the corresponding port 230; however, it will be appreciatedby those skilled in the art that the combination of the insert 210 andflow restrictor 220 can still have the desired flow varying effect. FIG.6 is a top view of the insert 210 in place on the flow restrictor 220,and it can be seen that a substantial area of each of the threeunblocked ports 230 is unobstructed. As the insert 210 may only modifythe exposed area of the ports 230 but otherwise does not affect thefunction of the flow restrictor 220, the insert 210 can be considered tobe part of the flow restrictor component of the tool 100. The flow head180, flow restrictor 220, and the optional insert 210 may be consideredto form part of a valve in the tool 100.

The valve housing 170 in turn may be connected to another component ofthe drill string, here indicated as lower sub 240. This component couldbe an adaptor for the drill bit of the drill string. Drilling fluidpassing from the motor 140 and through the valve section 160 enters theshaft or other passage 245 defined in the lower sub 240. The passage 245is thus in fluid communication with the shaft 105, subject to any flowvariations imposed by the operation of the various components of thetool 100.

In operation, drilling fluid passes through the mandrel 110 and invertersection 120, and on through the motor 140. The drilling fluid isreceived in cavities defined by the rotor 150 and stator 155, causingthe rotor 150 to turn in an eccentric motion. The motion of the rotor150 is transferred to the multi-port flow head 180, which in turnrotates in an eccentric manner on the insert 210 and/or flow restrictor220. As a result of the motion of the flow head 180, the ports 190 inthe flow head 180 move into and out of alignment with the ports 215, 230of the insert 210 and flow restrictor 220. The alignment can includeonly partial alignment, where only part of a given port 190 of the flowhead 180 coincides with the ports 215 and 230 and the remainder of theport 190 is blocked by a solid region of the insert 210 and/or flowrestrictor 220. In some cases the alignment may be a perfectly centeredalignment where the center of a port 190 is aligned with the center of aport 215 and a corresponding port 230, although if the area of the port215 or 230 is smaller than the area of the port 190, the port 190 willbe partially blocked by the insert 210 or flow restrictor 220. When aflow head port 190 is in alignment with the ports 215, 230, fluidcommunication is permitted through at least that part of the port 190that is not blocked. A port 190 is therefore not in alignment with aport 215, 230 when it is effectively completely blocked by the insert210 and/or flow restrictor 220. The movement of the port 190 out ofalignment with the ports 215, 230 thus constrains or restricts thedrilling fluid flow through the port 190. As the port 190 moves intoalignment with ports 215, 230, the flow through the port 190 increases.At the same time, other ports 190 may be moving out of or into alignmentwith other ports 215, 230 of the insert 210 and/or flow restrictor 220.

In the examples shown in FIGS. 4 and 6, four ports 190 are provided inthe flow head 180 and three ports 230 are provided are positioned on theflow restrictor 220 and the insert 210, an unequal, 4:3 ratio. Combinedwith the 7:8 lobe ratio between the rotor 150 and stator 155, aquasi-irregular effect is achieved, whereby consecutive cycles of therotor 150 in the stator can result in a different orientation of theflow head 180 with respect to the flow restrictor 220 at a givenposition of the flow head 180 in the rotational cycle. This isillustrated in FIG. 7, which shows three example orientations I, II, andIII of the flow head 180 from FIG. 4 superimposed on the flow restrictor220 and insert 210 of FIGS. 5 and 6. These orientations are shown asexamples only to demonstrate how the flow head 180 might be located insubstantially the same position with respect to the flow restrictor 220,yet have a different orientation, with the result that the degree ofalignment of each port 190 of the flow head 180 with ports 215, 230 ofthe insert 210 and/or flow restrictor 220 can vary in consecutivecycles. The combination of the varying orientation of the ports 190 andthe rotation of the flow head 180, compounded by the configurations ofthe ports 190, 215 and/or 230, creates a flow rate through the valvesection 160 that follows a complex, polyrhythmic pattern as the drillingfluid flows from the motor 140, through the valve section 160, and on tocomponents of the drill string downstream from the valve section 160.The varying flow rate therefore includes multiple pressure spikesfollowing this complex pattern within the shaft 105 and 245, causingresponsive action from the inverter 300 and producing responsive axialmovement in the drill string and a percussive effect when drilling.

The resultant complex, polyrhythmic pattern may be considered to bearrhythmic within a given cycle of the rotor 150 in the stator 155,depending on the particular configuration of the ports (i.e., thenumber, positions, sizes, and cross-sectional profiles) in the flow head190 and the insert 210 and/or flow restrictor 220. As noted above,consecutive cycles of the rotor 150 in the stator can result in adifferent orientation of the flow head 180 with respect to the flowrestrictor 220 at a given position of the flow head 180 in therotational cycle; this may be considered to be irregular or arrhythmicas between the consecutive cycles of the rotor. The pattern of fluidflow and the consequential percussive effect can assist in preventingdrill cuttings in the drilling fluid from settling in the drill string,freeing stuck objects from the wellbore during drilling. The resultantaxial movement can also assist in freeing the drill bit or othercomponents of the drilling string that may become stuck during drilling,by varying the tension along the drilling string. Generally, the fluidflow and pressure pattern resulting from operation of the tool 100improves the overall effect and efficiency of directional drilling, andcan potentially result in less drag and easier steering and penetration(with less force) of the drill bit, thereby allowing a greater drillingdistance to be achieved with less exertion than would otherwise berequired. With appropriate selection of the rotor/stator ratio and/orport configurations, the frequency of pressure spikes can be controlledand selected so as to reduce interference with measurement whiledrilling (MWD) or other equipment, compared to conventional directionaldrilling apparatuses, including other pulsing mechanisms. Theseselections may be influenced by the characteristics of the drillingfluid or other components used in the drilling operation. As explainedabove, the port configurations may be modified by changing the number,dimensions, and profiles of the ports; it may be noted, though, that itis most convenient to employ a circular profile (i.e., a cylindricalport), as this is most easily manufactured. The beneficial aspects ofthe present embodiments may be attained for both horizontal and verticaldrilling operations.

In summary, a drilling tool includes a housing defining a central cavityfor enabling the transmission of drilling fluid through the drillstring. A motor contained in the housing includes a rotor-statorassembly, the motor producing eccentric motion of the rotor. An inverteror shock absorbing assembly disposed along the housing upstream from themotor functions to expend and contract the central cavity in response tofluid pressure changes produced by the drilling fluid flow. A valveassembly, comprising a multi-port flow head that rotates under influenceof the motor and a multi-port flow restrictor, creates a varying patternof pressure spikes in the drilling fluid as the ports of the flow headmove into and out of alignment with the ports of the flow restrictor,which in turn induces a percussive effect and axial movement in thedrill string.

While one or more embodiments of this invention have been illustrated inthe accompanying drawings and described above, it will be evident tothose skilled in the art that changes and modifications can be madetherein without departing from the invention. For instance, the number,sizes, shapes, and areas of the ports in the flow head, insert, and flowrestrictor described herein can be modified as appropriate to accomplisha desired effect, or to accommodate particular equipment or drillingfluid. The invention includes all such variations and modifications asfall within the scope of the appended claims.

1. A drilling tool assembly for use in a drill string, the drilling toolassembly comprising: a motor comprising an eccentrically-driven rotor; aflow head comprising a plurality of ports permitting fluid communicationtherethrough, the flow head being coupled to a rotor of the motor to bedriven thereby in eccentric rotational motion; a flow restrictor influid communication with the flow head, the flow restrictor comprising aplurality of ports permitting fluid communication therethrough, the flowrestrictor being stationary with respect to the rotational motion of theflow head, wherein rotation of the flow head with respect to the flowrestrictor causes one or more of the plurality of ports of the flow headto enter into and out of alignment with one or more of the plurality ofports of the flow restrictor such that fluid flow through the ports ofthe flow head and the flow restrictor is varied in an irregular pattern,the irregular pattern comprising a pattern in which an orientation ofthe flow head at a defined position in a cycle of the rotor is differentbetween consecutive cycles of the rotor.
 2. The drilling tool assemblyof claim 1, wherein the flow head comprises a plurality of ports havingat least two different cross-sectional areas, and the flow restrictorcomprises a plurality of ports having at least two differentcross-sectional areas.
 3. The drilling tool assembly of claim 2, whereinthe motor comprises a progressive cavity pump having a multi-lobe statorand a multi-lobe rotor, the stator having a different number of lobesthan the rotor.
 4. The drilling tool assembly of claim 3, wherein theflow head has a different number of ports than the flow restrictor. 5.The drilling tool assembly of claim 4, wherein the irregular pattern isdependent upon at least: a lobe ratio of the motor; a configuration ofthe plurality of ports of the flow head; and a configuration of theplurality of ports of the flow restrictor.
 6. The drilling tool assemblyof claim 4, wherein a lobe ratio of the rotor to the stator is 7:8. 7.The drilling tool assembly of claim 1, further comprising an invertersection in fluid communication with the motor, the motor beingpositioned between the inverter section and the flow head, the invertersection controlling axial movement in the drill string.
 8. The drillingtool assembly of claim 1, wherein the flow restrictor comprises aninsert between the flow head and the flow restrictor, the insertcomprising ports permitting fluid communication between the flow headand ports of the flow restrictor.
 9. The drilling tool assembly of claim1, wherein the ports of the flow head and the ports of the flowrestrictor are cylindrical.
 10. A valve component for use in a drillstring, the valve component comprising: a flow head comprising aplurality of ports permitting fluid communication therethrough, theplurality of ports including ports of different sizes; a flow restrictorcomprising a plurality of ports permitting fluid communicationtherethrough, the plurality of ports including ports of different sizes;the plurality of ports of the flow head being arranged such thateccentric rotation of the flow head with respect to the flow restrictorcauses one or more of the plurality of ports of the flow head to enterinto and out of alignment with one or more of the plurality of ports ofthe flow restrictor, such that fluid flow through the ports of the flowhead and the flow restrictor is varied in an irregular pattern, theirregular pattern comprising a pattern in which an orientation of theflow head at a defined position in a cycle of the rotor is differentbetween consecutive cycles of the rotor.
 11. The valve component ofclaim 10, wherein the sizes of the ports of the flow restrictor aredifferent from the sizes of the ports of the flow head.
 12. The valvecomponent of claim 10, wherein the flow head is adapted to be driven byan eccentrically-driven rotor of a progressive cavity pump motor havinga multi-lobe rotor and a multi-lobe rotor, the stator having a differentnumber of lobes than the rotor.
 13. The valve component of claim 12,wherein the flow head has a different number of ports than the flowrestrictor.
 14. The valve component of claim 13, wherein irregularpattern is dependent upon at least: a lobe ratio of the motor; aconfiguration of the plurality of ports of the flow head; and aconfiguration of the plurality of ports of the flow restrictor.
 15. Thevalve component of claim 10, further comprising an insert between theflow head and the flow restrictor, the insert comprising portspermitting fluid communication between the flow head and ports of theflow restrictor.
 16. A method of varying drilling fluid pressure in adrill string, the method comprising: varying flow of the drilling fluidin the drilling string above a drilling tool of the drilling string inan irregular pattern, the irregular pattern being determined by flow ofthe drilling fluid through a flow head and a flow restrictor, the flowhead being driven by a rotor in eccentric rotation with respect to theflow restrictor, each of the flow head and the flow restrictorcomprising a plurality of ports, the plurality of ports in the flow headcomprising different sizes and the plurality of ports in the flowrestrictor comprising different sizes, wherein the flow of the drillingfluid is determined by alignment of any of the plurality of ports of theflow head with any of the plurality of ports of the flow restrictor, theirregular pattern comprising a pattern in which an orientation of theflow head at a defined position in a cycle of the rotor is differentbetween consecutive cycles of the rotor.
 17. The method of claim 16,wherein a variation in flow of the drilling fluid induces acorresponding variation in pressure in the drill string.
 18. The methodof claim 16, wherein the flow head comprises a number of ports of atleast two different sizes and the flow restrictor comprises a differentnumber of ports of at least two different sizes, the at least twodifferent sizes of the flow restrictor ports being different than thesizes of the flow head ports.
 19. The method of claim 16, wherein theflow head comprises at least three ports and the flow restrictorcomprises at least four ports, the rotor comprises a multi-lobe rotorthat moves in eccentric motion in a multi-lobe stator, a lobe ratio ofthe rotor to the stator being 7:8.